Matsya Purana — Iconographic Standards for the Navagrahas
धूम्रा द्विबाहवः सर्वे गदिनो विकृताननाः गृध्रासनगता नित्यं केतवः स्युर्वरप्रदाः //
dhūmrā dvibāhavaḥ sarve gadino vikṛtānanāḥ gṛdhrāsanagatā nityaṃ ketavaḥ syurvarapradāḥ //
All the Ketus are smoke-hued, two-armed, club-bearing, and fierce of face; ever seated upon a vulture-seat—yet they are said to be bestowers of boons.
It does not directly describe Pralaya; it belongs to the Matsya Purana’s omen-astrology (Ketu-lakshana), where celestial ‘ketus’ are characterized in form and function as portents that can still confer auspicious outcomes (boons).
By framing ketus as interpretable signs, it supports the king’s and householder’s duty to heed auspicious timings and omens via learned advisors (jyotiṣikas), aligning actions—such as campaigns, rites, or major undertakings—with indications that promise ‘vara’ (desired results).
No Vāstu rule is stated, but the verse gives a compact iconographic profile (color, arms, weapon, mount/seat) useful for ritual visualization and for identifying Ketu in jyotiṣa-based rites that seek protection or boon-granting outcomes.